Full-mold casting is one known method of forming metal products. In full-mold casting, a pattern is prepared that has the same shape as the metal product to be formed. The pattern is formed from a material that evaporates when it comes into contact with molten metal. When the evaporative pattern is packed inside a sand mold and molten metal is poured into the sand mold, the pattern will evaporate and be replaced with the molten metal. When the sand mold is destroyed after the molten metal has cooled, a cast product having the same shape as the pattern will be obtained.
Although full-mold casting is an excellent method for forming metal products having complex shapes, one problem is that it is difficult to fill the powder material that forms the sand mold around the evaporative pattern. In general, metal molds have complex shapes, therefore, the evaporative patterns for the metal molds have complex shapes. Cavities are easily formed around an evaporative pattern having a complex shape (i.e., spaces that are not filled with the powder material are left around the evaporative pattern) when the evaporative pattern is packed in a sand mold. Thus, difficult work will need to be continued over a long period of time in order to form a good sand mold.
A standard metal mold is formed by machining a metal blank, and comprises a mold surface that comes into contact with a work piece and a positioning surface that contacts the other side of the metal mold and adjusts the positional relationship with the other side of the metal mold. The metal blank on the back sides of the mold surface and the positioning surface plays a role in providing the mold surface, providing the positioning surface, and fixing the relative positional relationship between the mold surface and the positioning surface. Here, the portion that fixes the relative positional relationship between the mold surface and the positioning surface need not be a metal blank.
Patent Reference 1 discloses a press die that reinforces the lower die made of a plate with a lower frame, and reinforces the upper die made of a plate with an upper frame. The upper frame and lower frame used here are comprised of a plurality of bar-shaped members, as well as a three-dimensional mesh structure having connecting points that link the ends of the bar-shaped members and are distributed inside a three-dimensional space. By using a three-dimensional mesh structure instead of a metal blank, a product capable of being used as a metal mold can be achieved.